Illuminated instrument construction



.Aug.'l2, 195,8- J. N. DUPREE ILLUMINATED INSTRUMENT CONSTRUCTION Filed April 5. 1954 R44 ge JAMES N DUPREE,

IN VEN TOR. BY y \/%7f TmRN-K United States Patent() W ILLUMINATED INSTRUMENT coNsrRUcrIoN James N. Dupree, Hollywood, Calif., assigner to Ialifornia Plasteck, Inc., Los Angeles, Calif., a corporation Application April 5, '1954, Serial No. 420,947

Claims. (Cl. 116-4129) This invention relates to instruments, such as instruments mounted on an aircraft panel or the like, and is directed to the problem of combining with such an instrument a suitable lamp for illumination of the indicator element of the instrument as well as for illumination of the` indicia associated with the indicator element.

One requirement is that the illumination be effective for its purpose and yet be so subdued in character and so directed as to avoid glare and undesirable illumination of the `exterior environment of the instrument. The invention meets this requirement by providing ka lamp assembly or lamp housing adapted to be mounted ina central aperture in the light-transmitting face plate of the instrument and by restricting the emanation of light from the lamp housing to a window or Windows positioned'in the periphery of the central housing. While a single window of substantial circumferential extent may be provided, preferably the housing has a series of circumferentially spaced windows. The light source is a suitable lamp bulb in the housing so positioned relative to the housing windows as to cause the light to be emanated in a desired range of directions to illuminate both the region of the indicia and the region of the indicator element of the instrument.

A certain dilemma is involved in those instances in which the indicia are on the face plate of the instrument or immediately adjacent the face plate. On the one hand, ifall of the light is directed inward towards the interior ofthe instrument to avoid excessive illumination of the environment of the instrument, the indicia on or adjacent tothe `face plate will not be adequately illuminated; on the other hand, if any effective portion of the light is directed radially of the housing along the outer surface of the face plate for the sake of illuminating the indicia, the `result will be intolerably excessive illumination of the environment. In this regard it is to be borne in mind thatV often several such instruments are grouped together on a panel board and stray light from all of the instruments combines for an undesirable general illuminationv effect that may light up a whole cabin.

The invention solves this dilemma by placing the peripheralwindows of the lamp housing in position to extend rearward from a point in the central aperture of the face plate that lies between the two surface planes of the face plate. The lamp bulb is located in the housing with its filamentl in position to direct light radially outward into the edge of the aperture between these two surface planes. Thus, a substantial portion of the light is directed Vinto the interior of the instrument by the portions of the housing windows that extend inward from the inner surface of the face plate, and at the same time, a substantial portion of the light is directed into the material of theface plate edgewise thereof vby the forward portions of `the windows between the two `surface planes of the face plate.

The portion of light-thattenters the face plate edge- 2,846,970 Patented Aug. 12, 1958 ICC wise thereof does not cause glare or undesirable external' on the inner face of the face plate that is of light-scat-` tering character to make the indicia uniquely visible.y

A further feature of the preferred practice of the inven-` tion is the concept of surrounding the outer peripheral edge of the face plate with light-reflective material to co-operate with the inwardly reflecting face surfaces of the face plate. A still further feature is the provision of lter means at the windows of the housing to modify the emanated light.

By virtue vof this arrangement, the filter means` provides subdued emanated light of desirable wave lengths and a portion of the filtered light is trapped in an efficient system of reflecting surfaces to make indicia on the face plate plainly visible. portion of the filtered light is directed inwardly back of the face plate to make the indicator element or pointer of the instrument plainly visible. The preferred practice of the invention also includes the provision of a suitable lens in the path of the inwardly directed light for desirable redirecting and sufusion of the light that illuminates the indicator element.

Another problem to be met is to provide a lamp assembly of the described character that is adapted for mounting in the face plate aperture in such manner as to permit the instrument to be hermetically sealed and at the same time to permit convenient replacement of a lamp bulb when required. For this purpose, the invention provides a housing for mounting in the face plate aperture that engages both faces of the face plate to hold the housing in assembled position and the housing structure includes a closure member forward of the face plate that isremovable for full access to the interior of the housing.

A further problem is to provide for energization of the lamp bulb in the housing by a circuit outside the housing. In this regard, a feature of the invention is the housing is of laminated construction with outer and- 1nner conducting walls separated by a nonconducting This construction makes it possible for the outer wall. and inner conducting laminations of the housing to serve as part of the lamp circuit on oppositel sides of the lamp bulb. In this regard, a special feature of the preferred embodiment of the invention is the use of material forr the intermediate insulating wall that will serve the additional purpose of a light filter.

It is apparent from the foregoing that the inventionl may be embodied in the factory assembly of an instrument, or may be embodied in a combination of face plate and lamp assembly to be sold to manufacturers of instruments, or may be embodied in a lamp assembly as a separate article of manufacture adapted for mounting in a suitably apertured face plate.

The-'various features and advantages of the invention At the same time anotherv will be apparent in the following detailed description considered with the accompanying drawing.

In the drawing, which is to be regarded as merely illustrative:

Figure 1 is a View partly in side elevation and partly in section, illustrating a selected embodiment of the invention;

Figure 2 shows the interior of the instrument as viewed along the line 2 2 of Figure 1;

Figure 3 is an enlarged longitudinal section taken as indicated by the line 3-3 of Figure l; and

Figure 4 is a fragmentary section taken as indicated by the line 4 4 of Figure 3.

The selected embodiment of the invention illustrates the underlying principles as applied to the construction of an accelerometer. It will be apparent that this selected embodiment will provide adequate guidance for those skilled in the art who may have occasion to apply the same principles to other types of instruments.

The accelerometer shown in Figure 1 has a cup shaped case which is closed by a circular face plate 11 of light-transmitting material such as glass or suitable plastic. The sensing mechanism of the instrument controls a shaft 12 that carries an indicator element in the form of a hand or pointer, generally designated by numeral 15. Preferably the indicia associated with the movements of the pointer 15 are on the inner surface of the face plate 11. In this instance, the indicia comprises the usual numerals 16 and scale marks 17. It is contemplated that the indicia will ,be of material that will both reflect light and scatter light. Ordinary white paint has been found suitable for this purpose.

In accord with the invention, the face plate 11 has a central circular aperture 18 to receive a lamp assembly generally designated by numeral 20 and preferably the peripheral area of the face plate or outer edge of the face plate is coated with `a suitable layer 21 of light reiiecting material. The peripheral surface of the face plate 11 may be silvered for this purpose, but preferably the desired light-reflecting surface is provided by the application of heat to fuse a mixture of iinely divided silver and low melting powdered glass to the peripheral surface of the face plate. i

The lamp assembly 20 includes a housing body 24 of cylindrical configuration that is closed at its inner end by an end wall 25 integral therewith and is normally closed at its outer or forward end by a suitable closure member 26. The housing body 24 is adapted to receive a lamp bulb 27 which is positioned in the housing .body with its base end outward. In the construction shown, the lamp bulb 27 has an end Contact or terminal 30 for electrical connection with one side of a lamp circuit and has a base ferrule 31 which serves as a contact or terminal for electrical connection with the other side of the circuit. The base ferrule 31 is formed with a circumferential rib 32 which abuts against the outer end of the housing body 24 for -co-operation therewith to iix the longitudinal position of the lamp bulb in the housing member. In the preferred practice of the invention, this position of the lamp bulb 27 places the filament 33 of the lamp bulb between the planes of the outer and inner face surfaces of the face plate 11.

The housing body 24 is preferably of laminated construction comprising an inner metal shell 37 integral with the end wall 25, an intermediate insulating sleeve 38, and an outer :sleeve or bushing 413. The housing body 24 is provided with suitable windows, generally designated 41, that are spaced circumferentially with the outer ends of the windows between the surface planes of the face plate 11 and with the inner ends of the windows extending inward from the face plate. In the arrangement illustrated by the drawing, the outer ends of the windows 41 are approximately half way between the two surface planes of the face plate 11.

As shown in Figures 3 and 4, each of the windows 41 comprises an opening 42 in the inner shell 37 and a corresponding opening 43 in the outer housing 40. The intermediate insulating sleeve 38, which is bonded both to the inner shell 37 and the outer bushing 40, is of a suitable plastic material which will not only serve to insulate the inner sleeve and the outer bushing from each other, but also will serve as a filter for each of the windows 41. For this last purpose, the insulating sleeve is extended to span the window openings 42 and 43 of the inner shell and outer bushing respectively. The insulating sleeve may, for example, be made of a translucent red plastic material.

The outer bushing 40 of the housing body 24 is formed with a radial flange 44 for abutment against the inner face of the face plate 11 and preferably the ange 44 is formed with a circular shoulder 45 dimensioned for relatively lclose t in the aperture 18 in the face plate. It is contemplated that the radial flange 44 will be bonded to the inner surface of the face plate 11 and for this purpose a mixture of powdered silver and powdered low melting glass may be used, the mixture being heated `until it fuses both to the iiange 44 and to the face plate. A feature of the invention in this regard is that with the flange 44 fused to the face plate 11, the aperture 18 in the face plate will be eifectively hermetically sealed. This feature is of importance in those instances where it is desirable to maintain a-l vacuum inside the instrument and in those instances where it is desirable to confine a gaseous body in the instrument.

The closure member 26 is preferably in the form of a metal cap that threads onto the outer bushing 40 of the housing member 24, and that is suitably adapted to hold the lamp bulb 27 in its assembled position. In the construction shown, a suitable metal spring 46 is mounted in a recess 47 inside the closure member and is retained therein by a circular shoulder 43 that overhangs the recess. The spring carries a metal disc 511 which presses against the end contact or terminal 3i) of the lamp bulb. Preferably, the closure member 26 is covered by a cap 54 of non-conducting material which is bonded to the closure member and is adapted to contact a suitable sealing ring 55. The cap 54 is made of relatively rigid plastic material, such as hard rubber, and the sealing ring 55 may be made of any relatively soft rubber-like material.

It is apparent that the screw-threaded engagement of the closure member 26 with the housing body 24 makes possible sufficient pressure on the part of the plastic cap 54 against the sealing ring 55 to make the lamp assembly water proof. This feature is important, for example, where it is desirable to protect the interior of the lamp housing against an environment of high humidity.

It is also apparent that since the closure member 26 presses the sealing ring 55 against the outer face of the face plate 11, the closure member may co-operate with the radial flange 44 of the housing member 24, to grip the lopposite faces of the -face plate 11 and thereby clamp the lamp assembly 20 in position. Thus, the continuous bond between the radial flange 44 and the face plate may be `omitted in those instances where it is not necessary to seal `off the interior of the instrument from the atmosphere. It is also possible, if desired, to bond the sealing ring 55 to the periphery of the outer bushing 40 so that the sealing ring acting independently of the closure member 26 may cooperate with the radial flange 44 to grip the face plate from opposite sides to hold the lamp assembly in place.

In the preferred practice of the invention, the lamp assembly 2l) is adapted for connection with an energizing circuit by means of two conductors 56 and 57 that are bonded to the inner surface vof the face plate 11 on opposite sides of the lamp assembly. Each of these conductors 56 and 57 may be formed by fusing to the face plate a mixture of powdered silver and powdered low melting glass. The conductor 56 makes electrical connection directly with the radial flange 44 of the outer nushing 40 and the conductor 57 is electrically connected vith the inner metal shell 37 of the lamp assembly.

Preferably, the inner end of the lamp assembly is pro- /ided with a concave or dome-shaped lens 58 and the :onductor 57 is connected with the inner shell 37 through his lens. The lens 58, which is shaped to re-direct the light from the windows 41 in a desirable manner, is aonded to the inner surface of the radial flange 44 in any suitable manner. The lens may be bonded, for example, Jy means .of a fused mixture of powdered silver and aowdered glass. A suitable metal pin 60 extends through the lens 58 to the inner metal shell 37, the pin being bonded to the inner shell and being sealed in the lens. A fine wire 61 connects the metal pin 60 with the coniuctor 57.

From the foregoing it is apparent that one side of the lamp circuit includes: conductor 56; the outer bushing 40; closure member 26; and the spring 46 in abutment with the end contact or terminal 30 of the lamp aulb. The yother side of the -circuit includes: the con- :iuctor S7; the fine wire 61; the metal pin 60; and the Inner metal shell 37 in pressure contact with the rib 32 af the base ferrule 31 of the lamp bulb.

The manner in which the invention serves its purpose will be readily apparent from the foregoing description. Since the filament 33 of the lamp bulb and the outer ends of the series of windows 41 are intermediate the planes of the two surfaces of the face plate 11, light from the filament is directed into the face plate edgewise thereof from inside the aperture 18. All of the light that enters the :material of the face plate 11 in this manner is at exceedingly low angles relative to the two face surfaces of the face plate and therefore such light is reflected back into the interior of the face plate by the two face surfaces, instead of passing freely out-of the face plate. Some of the light that enters the face plate in this manner goes directly to the outer peripheral layer of lightreflecting material 21 and some of the light reaches this outer layer by reflection from the face surfaces of the face plate. The light that reaches the outer reflecting layer 21 is directed back towards the central area of the face plate. Thus, the face plate 11 is bounded by lightreflecting surfaces to constitute a trap for light from the filament 33 and the multiple reliections from the various surfaces results in a 4desirable diffusion and softening of the light. As a result, the indicia comprising the numeral 16 and the scale marks 17 on the inner surface of the face plate 11 are amply illuminated but no path is offered for direct passage of light from the filament 33 to the region in front of the face plate 11.

Light from the filament 33 also passes through the windows 41 and the lens -58 'directly into the interior of the instrument to illuminate the pointer 15. Preferably the pointer 15 is formed with an inclined offset 64 which is substantially normal to the rays of light from the [ilament 33, and is therefore well illuminated. This offset has the advantage of placing the end portion 65 of the pointer relatively close to the indicia on the face plate or at least closer than would -be possible otherwise in View of the presence of the lens 58 in the region of the base of the pointer.

My description of this selected embodiment of the invention by way of example and to illustrate the principles involved will suggest various changes, substitutions, and other departures from my disclosure that fall within the spirit and scope of the appended claims.

I claim:

1. In an instrument of the character described having a movable indicator element, the combination therewith of: a face plate for the instrument of light-transmitting material having an laperture therein; a lamp housing mounted in said aperture in said face plate and extending inward from the face plate, said housing being adapted t-o confine a lamp `and having at least one side window for illumination of the instrument by the lamp,

ment and a light-transmitting face plate forward therefrom, the combination of: `a lamp housing mounted in an aperture in said face plate with the housing extending both inwardly and outwardly from the face plate, said housing being open at its outer end to receive a lampv bulb with the base of the ybulb directed outward, said lamp housing having at least one window in the region of said face plate, said housing having an inner shell of conducting material to embrace the base of the lampV bulb; anchorage means of conducting material on said housing extending laterally therefrom in contact with the inner surface of said `face plate, said anchorage means being insulated from said inner shell; closure means of conducting material releasably mounted on the outer end of said housing, said closure means being normally electrically connected with said anchorage means; a metal spring inside said closure means to press against the outer base end of the lamp bulb; a conductor inwardly of said face plate in contact with said anchorage means and bonded to the inner surface of said face plate to connect one side' of a circuit to said lamp bulb through said closure means and said spring; a second conductor inwardly of said face plate` and bonded to the inner surface `of said face plate adapted to connect the other side of the circuit with the lamp bulb through said inner shell of the housing, and a lens at the inner end of said lamp housing, said second conductor extending through said lens to said inner shell of the lamp housing.

3. A lamp assembly for mounting in a circular aperture in the light-transmitting face plate of an instrument for energization of a lamp bulb inside the assembly by a pair of conductors positioned inwardly of the face plate, said lamp assembly including: a housing body adapted for mounting in said aperture, said housing'body having an inner shell of conducting material to enbrace the base of the lamp bulb; anchorage means of conducting material carried by said housing body and insulated` from said inner shell, said anchorage means extending laterally from the housing body for contact with the inner surface of said face plate; closure means of conducting material releasa'bly mounted on the outer end of said housing and insulated from said inner shell, said closure means being electrically connected with said anchorage means; a metal spring inside said closure means to press against the base end of the lamp bulb, `whereby one terminal of said lamp bulb may be electrically connected to one of said conductors through said spring, closure means, anchorage means; and means forelectrically connecting said shell with the other of said pair of conductors thereby to connect the other terminal of the lamp bulb therewith, a resilient sealing ring embracing said outer sleeve adjacent said closure means; and a cap of non-conducting material encasing said enclosure means f-or making sealing contact with said sealing ring.

4. A lamp assembly for mounting in a circular aperture in the light-transmitting face plate of an instrument for energization of a lamp bulb inside the assembly by a pair of conductors positioned inwardly of the face plate, said lamp assembly including: a metal s hell for positioning in said aperture, said shell having at least r one peripheral window positioned to extend inwardly from a plane between the two faces of said face plate to a plane spaced inward from the face plate, said shell being open at its outer end and 'being dimensioned to confine a lamp bulb with the base of the lamp directed outward in contact with the inner surface of the shell and with the iilament of the lamp between the planes of the surfaces of said face plate; an insulating sleeve having a continuous cylindrical wall embracing said shell; an outer sleeve of conducting material embracing said insulating sleeve, said outer sleeve being cut away in the region of said window, said shell and said two sleeves being united to form a housing body; anchorage means of conducting material extending laterally from said outer sleeve for abutment against the inner surface of said window; a closure member of conducting material releasably engaging the periphery of said outer sleeve to close the outer end 'of said housing body; and a metal spring in said closure member for contact with the end of said lamp bulb whereby said anchorage means may electrically connect one of said conductors with one terminal of said lamp bulb through said outer shell, closure means, and spring, and whereby said shell may electrically connect the other of said conductors with the other terminal of the lamp bulb.

5. A combination as set forth in claim 4 which includes a resilient sealing ring embracing said outer sleeve adjacent said closure means to `:zo-operate with the closure means for forming the seal; and in which said closure means is encased in a cap of non-conducting material for making sealing contact with said sealing ring.

6. A combination as set forth in claim 4 in which said insulating sleeve is of translucent material and extends over said Window to serve as a filter for light passing through the window.

7. A combination as set forth in claim 4 in which said anchorage means is a radial flange; and which includes a dome-shaped lens peripherally bonded to said flange.

8. A combination as set forth in claim 7 which includes conducting means extending from said shell through said lens to serve `as a terminal for connection with said other of said pair of conductors.

9. In an illuminated panel assembly which utilizes an electric lamp having an illuminating portion and further having a pair of electric contacts; the combination of: a panel of light transmitting material having a recess therein; an electrical conductor formed on one surface of the panel and extending across said one surface of the panel to a point adjacent the edge of the recess; electrically conductive bushing means extending into the recess in the panel and having a first end portion adapted for abutment with said one surface of said panel and for electrical contact with said conductor thereon, said bushing means having a second end portion projecting outwardly from the opposite surface of the panel, and said bushing means having at least one radial light transmitting window therein axially positioned to lie within the recess in the panel between the opposite surfaces of the panel; fastening means at said opposite surface of said panel engaging said second end portion of said bushing means; means for mounting the electric lamp in said bushing means with the illuminating portion of the lamp disposed within the recess in said panel to illuminate the interior of said panel through said radial light transmitting window in said bushing means, one of the electrical contacts of the lamp being in electrical connection with said bushing means; and means for establishing an electrical connection to the other electrical contact of the lamp.

10. In an illuminated panel assembly for utilizing an electric lamp having an illuminating portion and further having a pair of electric contacts, the combination of: an insulating panel of light transmitting material having an aperture extending therethrough; an electrical conducto-r formed on one surface of the panel and extending from an edge of the panel to a point adjacent the edge of the aperture; an electrically conductive cylindrical sleeve extending through said aperture in said panel and having an integral radial flange for abutment with said one surface of said panel and for electrical connection with said electrical conductor formed on said one surface, said sleeve -having a threaded end portion projecting `outwardly from the opposite surface of said panel, and said sleeve having a plurality of radial window openings therein axially positioned to lie within the aperture in the panel between said opposite surfaces thereof; fastening means at said opposite surface of said panel threadably engaging said threaded portion of said sleeve to clamp said radial flange of said sleeve firmly against said one surface of said panel and in electrical contact with said conductor; means for mounting the electric lamp in said sleeve with the illuminating portion of the lamp disposed Within the aperture in the panel and facing said one surface of the panel, and with one of the electrical contacts of the lamp in electrical connection with said sleeve; means for establishing an electrical connection to the other electrical contact of the lamp; and a tubular light lter of plastic material mounted coaxially with the lamp and with said sleeve, said light lter being axially aligned with said window openings in said sleeve.

References Cited in the tile of this patent UNITED STATES PATENTS 1,349,241 Walsh Aug. l0, 1920 2,172,765 Kollsman Sept. l2, 1939 2,401,867 Grimes June 1l, 1946 2,518,726 Shlenker Aug. 15, 1950 2,594,081 Shlenker Apr. 22, 1952 2,602,036 Sullivan July l, 1952 FOREIGN PATENTS 827,715 Germany Jan. 14, 1952 

